Impacts

Benchmark glaciers in the Himalayas keep receding

Benchmark glaciers in the Himalayas keep receding

The steady retreat of Satopanth and Bhagirath-Kharak, two glaciers that are closely monitored by scientists, is a chilling reminder of how climate change is affecting the hydrology of Ganga headwaters

The snout of the Bhagirath-Kharak glacier (Photo by Hridayesh Joshi)

Located just three km from the Hindu shrine of Badrinath, Mana is the last village near the India-China border. At a height of over 3,000 metres, Mana is a special attraction for pilgrims and tourists alike. Known for its condiments, handicraft and herbal tea, the village also has something special to offer. It is the gateway to an arduous walk to two important Himalayan glaciers — Satopanth and Bhagirath-Kharak. With enthusiastic trekkers trickling in, Mana remains abuzz for at least six months from May to October. However, these two glaciers are retreating, slowly and continuously.

Satopanth and Bhagirath-Kharak are among the most monitored and analysed glaciers in the Himalayas. Their snouts are separated by just 1.5 km. There is very little difference in their altitudes. Whereas Satopanth is situated at 3,870 metres, Bhagirath-Kharak is at 3,796 metres above mean sea level. The former is the origin of Alaknanda River and latter is the source of a stream called Uttar Ganga. Both watercourses merge after covering a short distance from their respective origins and the stream is then called Alaknanda, one of the largest tributaries of the Ganga.

The Satopanth lake in the Himalayas (Photo by Aditya Mishra)

Benchmark glaciers

These two mid-sized glaciers are termed benchmark glaciers in the scientific community because their length and size make them ideal for study. Their accessibility also makes it possible for researchers to conduct ground experiments. Interestingly, India’s famous Gangotri glacier isn’t a preferred glacier for field studies as it is too long at 30 km, whereas Satopanth and Bhagirath-Kharak are just 13 km and 18.5 km long, respectively.

“The size is crucial. Gangotri glacier, being too large, isn’t feasible for study and analysis because you can’t access it more than 3-4 km,” Harish Chandra Nainwal, Head of the Geology Department in Hemvati Nandan Bahuguna Garhwal University in Uttarakhand, told indiaclimatedialogue.net. “However, the situation is different at the Satopanth and Bhagirath-Kharak glaciers. They are average in size and length and much of the glaciers is accessible, which is an ideal scenario for any researcher.” Nainwal has been researching these two glaciers for more than 10 years.

Due to their inaccessibility, information about glaciers is often gathered by remote sensing technique. There are very few glaciers like Satopanth and Bhagirath-Kharak that are constantly monitored on the ground as well. “The fieldwork and ground validation of the information gathered by satellite is important and it is regularly being done here at Satopanth and Bhagirath-Kharak,” S.P. Sati, a geologist who is working in Himalayas for several years, told indiaclimatedialogue.net. Satopanth glacier is 21 sq. km in size, whereas the Bhagirath-Kharak is around 31 sq. km.

The study, which has Nainwal as lead author, also says official topographic maps are not entirely accurate. “Based on several old records and maps, we have presented evidence that while the glacier front of Satopanth Glacier and Bhagirath-Kharak glacier depicted in Survey of India (1962) topographic maps are inaccurate, the coordinates and elevation are fairly accurate,” it says. “This has led to revised estimates of the area vacated and snout retreat in last 57 years.”

Initially, the study of glaciers by Geological Survey of India (GSI) in 1960s and 1970s was mainly through remote sensing and focused on the position of snout of a glacier. Detecting the position of glacier’s snout annually was done to ascertain the rate at which a glacier was retreating, or in rare cases, advancing. “They tried to measure it (by satellite imaging) every year in several glaciers across the Himalayas but soon realised that it wasn’t the perfect way to know the health of a glacier,” said an expert during a recent Satopanth trek. “The measurement of net mass balance of glaciers is a much more reliable method to know the condition of a glacier.”

A glacier is divided in two zones — accumulation and ablation. Where snow and ice deposit is called the accumulation zone and where the loss of ice takes place due to melting and other reasons is known as the ablation zone. Mass balance is the difference of accumulation and ablation of snow on any glacier. An advancing glacier will have a positive mass balance because of net accumulation and a retreating glacier will have a negative mass balance due to more melting than deposit of snow.

Nainwal and his team initiated glaciological mass balance studies on Satopanth Glacier in 2013. Wooden stakes were installed in the ablation zone only because of frequent avalanches in the accumulation zone. The mass balance of Satopanth glacier is estimated to be minus (-) 2.0 m of water equivalent for 2015. The other estimates of mass balance for subsequent years are still being analysed and will be published next year. There are, however, no field measurements of mass balance for the Bhagirath Kharak glacier, mainly because of its vast extension, the researchers said.

Almost all the Himalayan glaciers are retreating, including Gangotri, Satopanth and Bhagirath-Kharak. The study with field research and ground validation has shown that the snouts of Satopanth and Bhagirath-Kharak glacier have retreated at a rate of 5.7 and 6.0 metres per year respectively. It is known that the Gangotri glacier has been retreating much faster. It retreated at a rate of 19 m every year between 1935 and 1999. However, in recent years, it is found that the rate of the retreat of Gangotri glacier has slowed down.

Moraine cover

While the experts have attributed the retreat of glaciers to the warming climate, they also say that the moraine cover helps the Himalayan glaciers to protect themselves from melting. Most of the glaciers are covered in moraine, unlike glaciers in Europe and Antarctica. More than 65% of Satopanth glacier’s total length is covered by moraine, which protects the glacier from melting by minimising the impact of direct sunlight.

Results show that both Satopanth and Bhagirath-Kharak are experiencing a similar warming climate but a regular avalanche-feed from snow peaks keeps adding to their mass. “There have been justified concerns for our glaciers,” Nainwal told indiaclimatedialogue.net. “We all know they are melting and retreating, but still they are not as unhealthy in given climatic conditions as they are shown in the media.”

There are various factors affecting the health of glaciers. In recent years, erratic rain and snowfall patterns have been observed more frequently in the Himalayan region. Experts say snow and rain are falling at an unexpected time, place and volume. This is affecting the health of glaciers. “Earlier, rain would not fall after a certain height, but now rain is happening even at the height of Satopanth and Bhagirath-Kharak glaciers,” Aditya Mishra, a research scholar who camps for more than six month a year at these glaciers, told indiaclimatedialogue.net. “Snowfall has decreased and it often takes place at a season when it is not expected or required.”

Rising temperature and its consequences are widely accepted phenomena across the globe. Peculiar things are happening at these heights in the Himalayas. For instance, at 4,350 metres, the moraine-dammed Satopanth Taal (lake) has shrunk significantly in the last few years. On the other hand, many new small lakes are forming at the top of glaciers. There are many reasons for this, but all are due to faster melting of Himalayan glaciers.

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